[be] Stabilize block ids

ghstack-source-id: 83aedf9f086ccb4819655eab803f25f944b75c7b
Pull Request resolved: https://github.com/facebook/react-forget/pull/2851

compiler/packages/babel-plugin-react-forget/src/Entrypoint/Pipeline.ts

@@ -66,6 +66,7 @@ import {
 import { alignMethodCallScopes } from "../ReactiveScopes/AlignMethodCallScopes";
 import { alignReactiveScopesToBlockScopesHIR } from "../ReactiveScopes/AlignReactiveScopesToBlockScopesHIR";
 import { pruneAlwaysInvalidatingScopes } from "../ReactiveScopes/PruneAlwaysInvalidatingScopes";
+import { stabilizeBlockIds } from "../ReactiveScopes/StabilizeBlockIds";
 import { eliminateRedundantPhi, enterSSA, leaveSSA } from "../SSA";
 import { inferTypes } from "../TypeInference";
 import {
@@ -366,6 +367,13 @@ function* runWithEnvironment(
     value: reactiveFunction,
   });
 
+  stabilizeBlockIds(reactiveFunction);
+  yield log({
+    kind: "reactive",
+    name: "StabilizeBlockIds",
+    value: reactiveFunction,
+  });
+
   const uniqueIdentifiers = renameVariables(reactiveFunction);
   yield log({
     kind: "reactive",

compiler/packages/babel-plugin-react-forget/src/ReactiveScopes/StabilizeBlockIds.ts

@@ -0,0 +1,80 @@
+import {
+  BlockId,
+  ReactiveFunction,
+  ReactiveScopeBlock,
+  ReactiveTerminalStatement,
+  makeBlockId,
+} from "../HIR";
+import { getOrInsertDefault } from "../Utils/utils";
+import { ReactiveFunctionVisitor, visitReactiveFunction } from "./visitors";
+
+export function stabilizeBlockIds(fn: ReactiveFunction): void {
+  const referenced: Set<BlockId> = new Set();
+  visitReactiveFunction(fn, new CollectReferencedLabels(), referenced);
+
+  const mappings = new Map<BlockId, BlockId>();
+  for (const blockId of referenced) {
+    mappings.set(blockId, makeBlockId(mappings.size));
+  }
+
+  visitReactiveFunction(fn, new RewriteBlockIds(), mappings);
+}
+
+class CollectReferencedLabels extends ReactiveFunctionVisitor<Set<BlockId>> {
+  override visitScope(scope: ReactiveScopeBlock, state: Set<BlockId>): void {
+    const { earlyReturnValue } = scope.scope;
+    if (earlyReturnValue != null) {
+      state.add(earlyReturnValue.label);
+    }
+    this.traverseScope(scope, state);
+  }
+  override visitTerminal(
+    stmt: ReactiveTerminalStatement,
+    state: Set<BlockId>
+  ): void {
+    if (stmt.label != null) {
+      if (!stmt.label.implicit) {
+        state.add(stmt.label.id);
+      }
+    }
+    this.traverseTerminal(stmt, state);
+  }
+}
+
+class RewriteBlockIds extends ReactiveFunctionVisitor<Map<BlockId, BlockId>> {
+  override visitScope(
+    scope: ReactiveScopeBlock,
+    state: Map<BlockId, BlockId>
+  ): void {
+    const { earlyReturnValue } = scope.scope;
+    if (earlyReturnValue != null) {
+      const rewrittenId = getOrInsertDefault(
+        state,
+        earlyReturnValue.label,
+        state.size
+      );
+      earlyReturnValue.label = makeBlockId(rewrittenId);
+    }
+    this.traverseScope(scope, state);
+  }
+  override visitTerminal(
+    stmt: ReactiveTerminalStatement,
+    state: Map<BlockId, BlockId>
+  ): void {
+    if (stmt.label != null) {
+      const rewrittenId = getOrInsertDefault(state, stmt.label.id, state.size);
+      stmt.label.id = makeBlockId(rewrittenId);
+    }
+
+    const terminal = stmt.terminal;
+    if (terminal.kind === "break" || terminal.kind === "continue") {
+      const rewrittenId = getOrInsertDefault(
+        state,
+        terminal.target,
+        state.size
+      );
+      terminal.target = makeBlockId(rewrittenId);
+    }
+    this.traverseTerminal(stmt, state);
+  }
+}

compiler/packages/babel-plugin-react-forget/src/ReactiveScopes/index.ts

@@ -33,6 +33,7 @@ export { pruneTemporaryLValues as pruneUnusedLValues } from "./PruneTemporaryLVa
 export { pruneUnusedLabels } from "./PruneUnusedLabels";
 export { pruneUnusedScopes } from "./PruneUnusedScopes";
 export { renameVariables } from "./RenameVariables";
+export { stabilizeBlockIds } from "./StabilizeBlockIds";
 export {
   ReactiveFunctionTransform,
   eachReactiveValueOperand,

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/block-scoping-switch-dead-code.expect.md

@@ -28,14 +28,14 @@ export const FIXTURE_ENTRYPOINT = {
 
 ```javascript
 function useHook(a, b) {
-  bb1: switch (a) {
+  bb0: switch (a) {
     case 1: {
       if (b == null) {
         return;
       }
 
       console.log(b);
-      break bb1;
+      break bb0;
     }
     case 2: {
       return;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/block-scoping-switch-variable-scoping.expect.md

@@ -44,10 +44,10 @@ function Component(props) {
     t1 = $[1];
   }
   const handlers = t1;
-  bb2: switch (props.test) {
+  bb0: switch (props.test) {
     case true: {
       console.log(handlers.value);
-      break bb2;
+      break bb0;
     }
     default: {
     }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/complex-while.expect.md

@@ -25,10 +25,10 @@ export const FIXTURE_ENTRYPOINT = {
 
 ```javascript
 function foo(a, b, c) {
-  bb1: if (a) {
+  bb0: if (a) {
     while (b) {
       if (c) {
-        break bb1;
+        break bb0;
       }
     }
   }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/conditional-break-labeled.expect.md

@@ -39,9 +39,9 @@ function Component(props) {
   if ($[0] !== props) {
     a = [];
     a.push(props.a);
-    bb1: {
+    bb0: {
       if (props.b) {
-        break bb1;
+        break bb0;
       }
 
       a.push(props.c);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/conditional-early-return.expect.md

@@ -76,12 +76,12 @@ function ComponentA(props) {
   let t0;
   if ($[0] !== props) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb8: {
+    bb0: {
       a_DEBUG = [];
       a_DEBUG.push(props.a);
       if (props.b) {
         t0 = null;
-        break bb8;
+        break bb0;
       }
 
       a_DEBUG.push(props.d);
@@ -130,13 +130,13 @@ function ComponentC(props) {
   let t0;
   if ($[0] !== props) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb8: {
+    bb0: {
       a = [];
       a.push(props.a);
       if (props.b) {
         a.push(props.c);
         t0 = null;
-        break bb8;
+        break bb0;
       }
 
       a.push(props.d);
@@ -163,13 +163,13 @@ function ComponentD(props) {
   let t0;
   if ($[0] !== props) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb8: {
+    bb0: {
       a = [];
       a.push(props.a);
       if (props.b) {
         a.push(props.c);
         t0 = a;
-        break bb8;
+        break bb0;
       }
 
       a.push(props.d);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/dominator.expect.md

@@ -49,23 +49,23 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 function Component(props) {
   let x = 0;
-  bb1: if (props.a) {
+  bb0: if (props.a) {
     x = 1;
   } else {
     if (props.b) {
     } else {
-      break bb1;
+      break bb0;
     }
 
     x = 3;
   }
-  bb10: bb12: switch (props.c) {
+  bb1: bb2: switch (props.c) {
     case "a": {
       x = 4;
-      break bb12;
+      break bb2;
     }
     case "b": {
-      break bb10;
+      break bb1;
     }
     case "c": {
     }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/early-return-nested-early-return-within-reactive-scope.expect.md

@@ -35,7 +35,7 @@ function Component(props) {
   let t0;
   if ($[0] !== props) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb12: {
+    bb0: {
       const x = [];
       if (props.cond) {
         x.push(props.a);
@@ -51,11 +51,11 @@ function Component(props) {
           const y = t1;
           x.push(y);
           t0 = x;
-          break bb12;
+          break bb0;
         }
 
         t0 = x;
-        break bb12;
+        break bb0;
       } else {
         let t1;
         if ($[4] === Symbol.for("react.memo_cache_sentinel")) {
@@ -65,7 +65,7 @@ function Component(props) {
           t1 = $[4];
         }
         t0 = t1;
-        break bb12;
+        break bb0;
       }
     }
     $[0] = props;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/early-return-no-declarations-reassignments-dependencies.expect.md

@@ -73,12 +73,12 @@ function Component(props) {
   let t0;
   if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb9: {
+    bb0: {
       const x = [];
       if (ENABLE_FEATURE) {
         x.push(42);
         t0 = x;
-        break bb9;
+        break bb0;
       } else {
         console.log("fallthrough");
       }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/early-return-within-reactive-scope.expect.md

@@ -49,12 +49,12 @@ function Component(props) {
   let t0;
   if ($[0] !== props) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb9: {
+    bb0: {
       const x = [];
       if (props.cond) {
         x.push(props.a);
         t0 = x;
-        break bb9;
+        break bb0;
       } else {
         let t1;
         if ($[2] !== props.b) {
@@ -65,7 +65,7 @@ function Component(props) {
           t1 = $[3];
         }
         t0 = t1;
-        break bb9;
+        break bb0;
       }
     }
     $[0] = props;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/inverted-if-else.expect.md

@@ -27,10 +27,10 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 function foo(a, b, c) {
   let x;
-  bb1: {
+  bb0: {
     if (a) {
       x = b;
-      break bb1;
+      break bb0;
     }
 
     x = c;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/inverted-if.expect.md

@@ -31,10 +31,10 @@ function foo(a, b, c, d) {
   let y;
   if ($[0] !== a || $[1] !== b || $[2] !== c || $[3] !== d) {
     y = [];
-    bb1: if (a) {
+    bb0: if (a) {
       if (b) {
         y.push(c);
-        break bb1;
+        break bb0;
       }
 
       y.push(d);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/labeled-break-within-label-loop.expect.md

@@ -35,9 +35,9 @@ function useHook(end) {
     log = [];
     for (let i = 0; i < end + 1; i++) {
       log.push(`${i} @A`);
-      bb6: {
+      bb0: {
         if (i === end) {
-          break bb6;
+          break bb0;
         }
 
         log.push(`${i} @B`);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/labeled-break-within-label-switch.expect.md

@@ -41,9 +41,9 @@ function useHook(cond) {
     switch (CONST_STRING0) {
       case CONST_STRING0: {
         log.push(`@A`);
-        bb3: {
+        bb0: {
           if (cond) {
-            break bb3;
+            break bb0;
           }
 
           log.push(`@B`);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/object-mutated-in-consequent-alternate-both-return.expect.md

@@ -33,16 +33,16 @@ function Component(props) {
   let t0;
   if ($[0] !== props) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb9: {
+    bb0: {
       const object = makeObject_Primitives();
       if (props.cond) {
         object.value = 1;
         t0 = object;
-        break bb9;
+        break bb0;
       } else {
         object.value = props.value;
         t0 = object;
-        break bb9;
+        break bb0;
       }
     }
     $[0] = props;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/partial-early-return-within-reactive-scope.expect.md

@@ -35,12 +35,12 @@ function Component(props) {
   let t0;
   if ($[0] !== props) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb12: {
+    bb0: {
       const x = [];
       if (props.cond) {
         x.push(props.a);
         t0 = x;
-        break bb12;
+        break bb0;
       } else {
         let t1;
         if ($[3] === Symbol.for("react.memo_cache_sentinel")) {
@@ -52,7 +52,7 @@ function Component(props) {
         y = t1;
         if (props.b) {
           t0 = undefined;
-          break bb12;
+          break bb0;
         }
       }
     }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/preserve-memo-validation/useMemo-conditional-access-own-scope.expect.md

@@ -32,7 +32,7 @@ function Component(t0) {
   const $ = useMemoCache(2);
   const { propA, propB } = t0;
   let t1;
-  bb6: {
+  bb0: {
     if (propA) {
       let t2;
       if ($[0] !== propB.x.y) {
@@ -43,7 +43,7 @@ function Component(t0) {
         t2 = $[1];
       }
       t1 = t2;
-      break bb6;
+      break bb0;
     }
     t1 = undefined;
   }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-switch.expect.md

@@ -55,10 +55,10 @@ function Component(props) {
   const c = [a];
 
   let x;
-  bb1: switch (c[0][0]) {
+  bb0: switch (c[0][0]) {
     case true: {
       x = 1;
-      break bb1;
+      break bb0;
     }
     default: {
       x = 2;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-switch-case-test.expect.md

@@ -47,14 +47,14 @@ import { unstable_useMemoCache as useMemoCache } from "react";
 function Component(props) {
   const $ = useMemoCache(2);
   let x;
-  bb1: switch (props.cond) {
+  bb0: switch (props.cond) {
     case true: {
       x = 1;
-      break bb1;
+      break bb0;
     }
     case false: {
       x = 2;
-      break bb1;
+      break bb0;
     }
     default: {
       x = 3;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-switch-condition.expect.md

@@ -48,10 +48,10 @@ function Component(t0) {
   const $ = useMemoCache(2);
   const { value } = t0;
   let x;
-  bb1: switch (GLOBAL) {
+  bb0: switch (GLOBAL) {
     case value: {
       x = 1;
-      break bb1;
+      break bb0;
     }
     default: {
       x = 2;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reassignment-separate-scopes.expect.md

@@ -62,7 +62,7 @@ function foo(a, b, c) {
     t0 = $[3];
   }
   const y = t0;
-  bb3: switch (b) {
+  bb0: switch (b) {
     case 0: {
       if ($[4] !== b) {
         x = [];
@@ -72,7 +72,7 @@ function foo(a, b, c) {
       } else {
         x = $[5];
       }
-      break bb3;
+      break bb0;
     }
     default: {
       if ($[6] !== c) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-cond-deps-break-in-scope.expect.md

@@ -36,9 +36,9 @@ function useFoo(t0) {
   let x;
   if ($[0] !== objIsNull || $[1] !== obj) {
     x = [];
-    bb1: {
+    bb0: {
       if (objIsNull) {
-        break bb1;
+        break bb0;
       } else {
         x.push(obj.a);
       }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-cond-deps-return-in-scope.expect.md

@@ -35,11 +35,11 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== objIsNull || $[1] !== obj) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb9: {
+    bb0: {
       x = [];
       if (objIsNull) {
         t1 = undefined;
-        break bb9;
+        break bb0;
       } else {
         x.push(obj.a);
       }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/cfg-switch-exhaustive.expect.md

@@ -44,14 +44,14 @@ function useCondDepInSwitch(props, other) {
   let x;
   if ($[0] !== other || $[1] !== props.a.b) {
     x = {};
-    bb1: switch (identity(other)) {
+    bb0: switch (identity(other)) {
       case 1: {
         x.a = props.a.b;
-        break bb1;
+        break bb0;
       }
       case 2: {
         x.b = props.a.b;
-        break bb1;
+        break bb0;
       }
       default: {
         x.c = props.a.b;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/cfg-switch-missing-case.expect.md

@@ -43,14 +43,14 @@ function useCondDepInSwitchMissingCase(props, other) {
   let x;
   if ($[0] !== other || $[1] !== props) {
     x = {};
-    bb1: switch (identity(other)) {
+    bb0: switch (identity(other)) {
       case 1: {
         x.a = props.a.b;
-        break bb1;
+        break bb0;
       }
       case 2: {
         x.b = 42;
-        break bb1;
+        break bb0;
       }
       default: {
         x.c = props.a.b;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/cfg-switch-missing-default.expect.md

@@ -40,10 +40,10 @@ function useCondDepInSwitchMissingDefault(props, other) {
   let x;
   if ($[0] !== other || $[1] !== props) {
     x = {};
-    bb1: switch (identity(other)) {
+    bb0: switch (identity(other)) {
       case 1: {
         x.a = props.a.b;
-        break bb1;
+        break bb0;
       }
       case 2: {
         x.b = props.a.b;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-poisoned/break-in-scope.expect.md

@@ -38,9 +38,9 @@ function useFoo(t0) {
   let x;
   if ($[0] !== objIsNull || $[1] !== obj) {
     x = [];
-    bb1: {
+    bb0: {
       if (objIsNull) {
-        break bb1;
+        break bb0;
       }
 
       x.push(obj.a);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-poisoned/break-poisons-outer-scope.expect.md

@@ -44,9 +44,9 @@ function useFoo(t0) {
   let x;
   if ($[0] !== cond || $[1] !== input) {
     x = [];
-    bb1: {
+    bb0: {
       if (cond) {
-        break bb1;
+        break bb0;
       }
       let t1;
       if ($[3] !== input.a.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-poisoned/reduce-if-nonexhaustive-poisoned-deps.expect.md

@@ -46,12 +46,12 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== cond || $[1] !== hasAB || $[2] !== input) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb11: {
+    bb0: {
       x = [];
       if (cond) {
         if (!hasAB) {
           t1 = null;
-          break bb11;
+          break bb0;
         }
         let t2;
         if ($[5] !== input.a.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-poisoned/reduce-if-nonexhaustive-poisoned-deps1.expect.md

@@ -47,12 +47,12 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== cond || $[1] !== hasAB || $[2] !== input) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb12: {
+    bb0: {
       x = [];
       if (cond) {
         if (!hasAB) {
           t1 = null;
-          break bb12;
+          break bb0;
         } else {
           let t2;
           if ($[5] !== input.a.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-poisoned/return-in-scope.expect.md

@@ -37,11 +37,11 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== objIsNull || $[1] !== obj) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb8: {
+    bb0: {
       x = [];
       if (objIsNull) {
         t1 = undefined;
-        break bb8;
+        break bb0;
       }
 
       x.push(obj.b);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-poisoned/return-poisons-outer-scope.expect.md

@@ -43,11 +43,11 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== cond || $[1] !== input) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb8: {
+    bb0: {
       x = [];
       if (cond) {
         t1 = null;
-        break bb8;
+        break bb0;
       }
       let t2;
       if ($[4] !== input.a.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-unpoisoned/else-branch-scope-unpoisoned.expect.md

@@ -45,8 +45,8 @@ function useFoo(t0) {
   let x;
   if ($[0] !== cond || $[1] !== input) {
     x = [];
-    bb1: if (cond) {
-      break bb1;
+    bb0: if (cond) {
+      break bb0;
     } else {
       let t1;
       if ($[3] !== input.a.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-unpoisoned/jump-target-within-scope-label.expect.md

@@ -40,8 +40,8 @@ function useFoo(t0) {
   let x;
   if ($[0] !== cond || $[1] !== input.a.b) {
     x = [];
-    bb1: if (cond) {
-      break bb1;
+    bb0: if (cond) {
+      break bb0;
     }
 
     x.push(input.a.b);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-unpoisoned/reduce-if-exhaustive-nonpoisoned-deps.expect.md

@@ -37,7 +37,7 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== hasAB || $[1] !== input.a || $[2] !== returnNull) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb11: {
+    bb0: {
       x = [];
       if (!hasAB) {
         let t2;
@@ -51,7 +51,7 @@ function useFoo(t0) {
         x.push(t2);
         if (!returnNull) {
           t1 = null;
-          break bb11;
+          break bb0;
         }
       } else {
         let t2;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/jump-unpoisoned/reduce-if-exhaustive-nonpoisoned-deps1.expect.md

@@ -47,7 +47,7 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== cond1 || $[1] !== cond2 || $[2] !== input.a.b) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb12: {
+    bb0: {
       x = [];
       if (cond1) {
         if (!cond2) {
@@ -61,7 +61,7 @@ function useFoo(t0) {
           }
           x.push(t2);
           t1 = null;
-          break bb12;
+          break bb0;
         } else {
           let t2;
           if ($[7] !== input.a.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reduce-reactive-deps/reduce-if-exhaustive-poisoned-deps.expect.md

@@ -38,7 +38,7 @@ function useFoo(t0) {
   let t1;
   if ($[0] !== inputHasABC || $[1] !== input.a || $[2] !== inputHasAB) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb11: {
+    bb0: {
       x = [];
       if (!inputHasABC) {
         let t2;
@@ -52,7 +52,7 @@ function useFoo(t0) {
         x.push(t2);
         if (!inputHasAB) {
           t1 = null;
-          break bb11;
+          break bb0;
         }
         let t3;
         if ($[7] !== input.a.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/repro-no-declarations-in-reactive-scope-with-early-return.expect.md

@@ -46,7 +46,7 @@ function Component() {
   let t2;
   if ($[0] !== items) {
     t2 = Symbol.for("react.early_return_sentinel");
-    bb15: {
+    bb0: {
       let t3;
       if ($[4] === Symbol.for("react.memo_cache_sentinel")) {
         t3 = (t4) => {
@@ -72,7 +72,7 @@ function Component() {
           t4 = $[5];
         }
         t2 = t4;
-        break bb15;
+        break bb0;
       }
       let t4;
       if ($[6] === Symbol.for("react.memo_cache_sentinel")) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/repro-no-value-for-temporary-reactive-scope-with-early-return.expect.md

@@ -43,12 +43,12 @@ function Component(props) {
   let t1;
   if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
     t1 = Symbol.for("react.early_return_sentinel");
-    bb8: {
+    bb0: {
       const object = makeObject_Primitives();
       const cond = makeObject_Primitives();
       if (!cond) {
         t1 = null;
-        break bb8;
+        break bb0;
       }
 
       t0 = (

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/repro-preds-undefined-try-catch-return-primitive.expect.md

@@ -37,15 +37,15 @@ import { useMemo } from "react";
 const checkforTouchEvents = true;
 function useSupportsTouchEvent() {
   let t0;
-  bb15: {
+  bb0: {
     if (checkforTouchEvents) {
       try {
         document.createEvent("TouchEvent");
         t0 = true;
-        break bb15;
+        break bb0;
       } catch {
         t0 = false;
-        break bb15;
+        break bb0;
       }
     }
     t0 = undefined;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/repro-renaming-conflicting-decls.expect.md

@@ -51,12 +51,12 @@ function Component(props) {
   let t2;
   if ($[0] !== props) {
     t2 = Symbol.for("react.early_return_sentinel");
-    bb11: {
+    bb0: {
       t0 = toJSON(props);
       const propsString = t0;
       if (propsString.length <= 2) {
         t2 = null;
-        break bb11;
+        break bb0;
       }
 
       t1 = identity(propsString);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/repro-unreachable-code-early-return-in-useMemo.expect.md

@@ -52,10 +52,10 @@ function Component(t0) {
   const $ = useMemoCache(7);
   const { value } = t0;
   let t1;
-  bb13: {
+  bb0: {
     if (value == null) {
       t1 = null;
-      break bb13;
+      break bb0;
     }
     try {
       let t3;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reverse-postorder.expect.md

@@ -43,12 +43,12 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 function Component(props) {
   if (props.cond) {
-    bb3: switch (props.test) {
+    bb0: switch (props.test) {
       case 0: {
-        break bb3;
+        break bb0;
       }
       case 1: {
-        break bb3;
+        break bb0;
       }
       case 2: {
       }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/ssa-switch.expect.md

@@ -34,12 +34,12 @@ export const FIXTURE_ENTRYPOINT = {
 
 ```javascript
 function foo() {
-  bb1: switch (1) {
+  bb0: switch (1) {
     case 1: {
-      break bb1;
+      break bb0;
     }
     case 2: {
-      break bb1;
+      break bb0;
     }
     default: {
     }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/switch-non-final-default.expect.md

@@ -38,9 +38,9 @@ function Component(props) {
   let y;
   if ($[0] !== props) {
     x = [];
-    bb1: switch (props.p0) {
+    bb0: switch (props.p0) {
       case 1: {
-        break bb1;
+        break bb0;
       }
       case true: {
         x.push(props.p2);
@@ -54,7 +54,7 @@ function Component(props) {
         y = t0;
       }
       default: {
-        break bb1;
+        break bb0;
       }
       case false: {
         y = x;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/switch-with-fallthrough.expect.md

@@ -42,16 +42,16 @@ export const FIXTURE_ENTRYPOINT = {
 
 ```javascript
 function foo(x) {
-  bb1: switch (x) {
+  bb0: switch (x) {
     case 0: {
     }
     case 1: {
     }
     case 2: {
-      break bb1;
+      break bb0;
     }
     case 3: {
-      break bb1;
+      break bb0;
     }
     case 4: {
     }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/try-catch-in-nested-scope.expect.md

@@ -0,0 +1,92 @@
+
+## Input
+
+```javascript
+import { mutate, setProperty, throwErrorWithMessageIf } from "shared-runtime";
+
+function useFoo({ value, cond }) {
+  let y = [value];
+  let x = { cond };
+
+  try {
+    mutate(x);
+    throwErrorWithMessageIf(x.cond, "error");
+  } catch {
+    setProperty(x, "henderson");
+    return x;
+  }
+  setProperty(x, "nevada");
+  y.push(x);
+
+  return y;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [{ value: 4, cond: true }],
+  sequentialRenders: [
+    { value: 4, cond: true },
+    { value: 5, cond: true },
+    { value: 5, cond: false },
+  ],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+import { mutate, setProperty, throwErrorWithMessageIf } from "shared-runtime";
+
+function useFoo(t0) {
+  const $ = useMemoCache(3);
+  const { value, cond } = t0;
+  let t1;
+  if ($[0] !== value || $[1] !== cond) {
+    t1 = Symbol.for("react.early_return_sentinel");
+    bb0: {
+      const y = [value];
+      const x = { cond };
+      try {
+        mutate(x);
+        throwErrorWithMessageIf(x.cond, "error");
+      } catch {
+        setProperty(x, "henderson");
+        t1 = x;
+        break bb0;
+      }
+
+      setProperty(x, "nevada");
+      y.push(x);
+
+      t1 = y;
+      break bb0;
+    }
+    $[0] = value;
+    $[1] = cond;
+    $[2] = t1;
+  } else {
+    t1 = $[2];
+  }
+  if (t1 !== Symbol.for("react.early_return_sentinel")) {
+    return t1;
+  }
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [{ value: 4, cond: true }],
+  sequentialRenders: [
+    { value: 4, cond: true },
+    { value: 5, cond: true },
+    { value: 5, cond: false },
+  ],
+};
+
+```
+      
+### Eval output
+(kind: ok) {"cond":true,"wat0":"joe","wat1":"henderson"}
+{"cond":true,"wat0":"joe","wat1":"henderson"}
+[5,{"cond":false,"wat0":"joe","wat1":"nevada"}]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/try-catch-in-nested-scope.ts

@@ -0,0 +1,28 @@
+import { mutate, setProperty, throwErrorWithMessageIf } from "shared-runtime";
+
+function useFoo({ value, cond }) {
+  let y = [value];
+  let x = { cond };
+
+  try {
+    mutate(x);
+    throwErrorWithMessageIf(x.cond, "error");
+  } catch {
+    setProperty(x, "henderson");
+    return x;
+  }
+  setProperty(x, "nevada");
+  y.push(x);
+
+  return y;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [{ value: 4, cond: true }],
+  sequentialRenders: [
+    { value: 4, cond: true },
+    { value: 5, cond: true },
+    { value: 5, cond: false },
+  ],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/try-catch-try-value-modified-in-catch.expect.md

@@ -34,7 +34,7 @@ function Component(props) {
   let t0;
   if ($[0] !== props.y || $[1] !== props.e) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb19: {
+    bb0: {
       try {
         const y = [];
         y.push(props.y);
@@ -43,11 +43,11 @@ function Component(props) {
         const e = t1;
         e.push(props.e);
         t0 = e;
-        break bb19;
+        break bb0;
       }
 
       t0 = null;
-      break bb19;
+      break bb0;
     }
     $[0] = props.y;
     $[1] = props.e;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/try-catch-with-catch-param.expect.md

@@ -35,7 +35,7 @@ function Component(props) {
   let t0;
   if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb12: {
+    bb0: {
       const x = [];
       try {
         throwInput(x);
@@ -43,11 +43,11 @@ function Component(props) {
         const e = t1;
         e.push(null);
         t0 = e;
-        break bb12;
+        break bb0;
       }
 
       t0 = x;
-      break bb12;
+      break bb0;
     }
     $[0] = t0;
   } else {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/try-catch-with-return.expect.md

@@ -37,19 +37,19 @@ function Component(props) {
   let t0;
   if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
     t0 = Symbol.for("react.early_return_sentinel");
-    bb26: {
+    bb0: {
       x = [];
       try {
         const y = shallowCopy({});
         if (y == null) {
           t0 = undefined;
-          break bb26;
+          break bb0;
         }
 
         x.push(throwInput(y));
       } catch {
         t0 = null;
-        break bb26;
+        break bb0;
       }
     }
     $[0] = x;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/unlabeled-break-within-label-switch.expect.md

@@ -38,11 +38,11 @@ function useHook(cond) {
   let log;
   if ($[0] !== cond) {
     log = [];
-    bb1: switch (CONST_STRING0) {
+    bb0: switch (CONST_STRING0) {
       case CONST_STRING0: {
         log.push(`@A`);
         if (cond) {
-          break bb1;
+          break bb0;
         }
 
         log.push(`@B`);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/useMemo-if-else-multiple-return.expect.md

@@ -21,7 +21,7 @@ import { unstable_useMemoCache as useMemoCache } from "react";
 function Component(props) {
   const $ = useMemoCache(4);
   let t0;
-  bb7: {
+  bb0: {
     if (props.cond) {
       let t1;
       if ($[0] !== props.a) {
@@ -32,7 +32,7 @@ function Component(props) {
         t1 = $[1];
       }
       t0 = t1;
-      break bb7;
+      break bb0;
     }
     let t1;
     if ($[2] !== props.b) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/useMemo-inlining-block-return.expect.md

@@ -26,7 +26,7 @@ import { unstable_useMemoCache as useMemoCache } from "react";
 function component(a, b) {
   const $ = useMemoCache(2);
   let t0;
-  bb6: {
+  bb0: {
     if (a) {
       let t1;
       if ($[0] !== b) {
@@ -37,7 +37,7 @@ function component(a, b) {
         t1 = $[1];
       }
       t0 = t1;
-      break bb6;
+      break bb0;
     }
     t0 = undefined;
   }

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/useMemo-inverted-if.expect.md

@@ -28,14 +28,14 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 function Component(props) {
   let t0;
-  bb10: {
-    bb2: {
+  bb0: {
+    bb1: {
       if (props.cond) {
-        break bb2;
+        break bb1;
       }
 
       t0 = props.a;
-      break bb10;
+      break bb0;
     }
 
     t0 = props.b;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/useMemo-multiple-if-else.expect.md

@@ -34,7 +34,7 @@ import { useMemo, unstable_useMemoCache as useMemoCache } from "react";
 function Component(props) {
   const $ = useMemoCache(3);
   let t0;
-  bb9: {
+  bb0: {
     let y;
     if ($[0] !== props) {
       y = [];
@@ -43,7 +43,7 @@ function Component(props) {
       }
       if (props.cond2) {
         t0 = y;
-        break bb9;
+        break bb0;
       }
 
       y.push(props.b);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/useMemo-switch-no-fallthrough.expect.md

@@ -29,10 +29,10 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 function Component(props) {
   let t0;
-  bb8: switch (props.key) {
+  bb0: switch (props.key) {
     case "key": {
       t0 = props.value;
-      break bb8;
+      break bb0;
     }
     default: {
       t0 = props.defaultValue;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/useMemo-switch-return.expect.md

@@ -35,16 +35,16 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 function Component(props) {
   let t0;
-  bb10: {
+  bb0: {
     let y;
-    bb2: switch (props.switch) {
+    bb1: switch (props.switch) {
       case "foo": {
         t0 = "foo";
-        break bb10;
+        break bb0;
       }
       case "bar": {
         y = "bar";
-        break bb2;
+        break bb1;
       }
       default: {
         y = props.y;

compiler/packages/snap/src/sprout/shared-runtime.ts

@@ -157,6 +157,12 @@ export function throwInput(x: Object): never {
   throw x;
 }
 
+export function throwErrorWithMessageIf(cond: boolean, message: string): void {
+  if (cond) {
+    throw new Error(message);
+  }
+}
+
 export function logValue<T>(value: T): void {
   console.log(value);
 }